A recent acquisition is a K-Line Burlington Northern Smoking Caboose. It is nicely detailed, has interior and exterior lighting, and a smoke unit. Not thinking much about it, I put it on my track and powered it up...in command mode...all 18 volts. The smoke unit smoked really well...REALLY well! And it kinda smelled like burn. Not good. I turned it off, put some more smoke fluid in, tried again. Same thing. Well this puts out way too much smoke, I said, so I flipped the switch on the bottom to turn the smoke unit off. It took a back burner.
Then someone recently posted on the OGR forum that the exact thing happened to him. Interesting. Long story short, these K-Line cabooses were made to run on more like 12 volts than 18 volts. A fellow forum member suggested installing some 3-amp diodes in-line on the hot wires on the 2 pickup rollers, orienting the diodes similarly in relation to the load (aka smoke unit and lights). These diodes would absorb or cut out the one phase of the AC current, effectively leaving 1/2 the voltage. I could apply 18 volts to the track but only 9 volts would make it to the internal electrical parts of the caboose. So I set out to do just that as an evening project.
I took the the shell off by taking 4 small phillips screws out of the bottom. The most difficult part of the whole job was dealing with the ladders on the end and the related walkways on the roof. The ladder tops go through the walkways and into the roof of the caboose, and the walkways are held to the roof by the tiniest screw-nails known to man. You will lose them. Why I didn't, I don't know. I attempted a photo of one sticking down through the walkway.
Once inside, I removed the shrink tubing and cut the hot wires from each pickup roller. I soldered in the 3a diodes in the same relative direction on each pickup wire as shown, far left and right.
I then taped up the connections with electrical tape and re-assembled...and put those tiny screw-nails back in place.
It works great! The fully-assembled photo shows it smoking, running off of 18v of track power with the diodes installed.
As all my electrical projects, I'm sure it wouldn't obtain a UL Listing, but mission accomplished anyway.
Total basement time: approx. 1 hour